Lightweight roll-top compression sackThe eVAC Dry Sack is a slimmed down version of Sea to Summit's award-winning eVENT Compression Dry Sack. They use waterproof, air-permeable eVENT fabric on the base for valve-free air expelling, allowing compact packing. Instead of straps for compression, you just roll the sack down and air is pushed out of the base. Then close the buckle and youve just saved space and weight. The sack is oval-shaped rather than round, so they resist rolling when laid on their side.